A large variety of electrical appliances are found in every home. While the presence of those appliances ensures that tasks are performed more safely and efficiently, the effectiveness of those appliances depends on controlling and indicating their operational status. For example, if an appliance is left turned on long after the user has finished with it, a child or careless adult may burn themselves on the exposed heated surfaces. Hence, an automatic control for shutting off the appliance as well as for indicating that the appliance has been shut off would avoid this and other safety risks. In addition, the controller/indicator would reduce additional wear and tear on the appliance, as well as save electricity.
Another problem created by the absence of indicators or controls stems from the fact that appliances often require a short period of time to reach a ready or operational state. In such instances, the user must periodically test the appliance to see if it is ready. By providing a control circuit for and indicator of a ready state, however, the user avoids losing the time spent testing the appliance.
Although some appliances are equipped with control and indicating circuitry that automatically turns the appliance off or indicates that the appliance is ready to use, such circuits have tended to involve relatively complex designs that have not fully solved the problems discussed above. Moreover, the appliances known in the prior art do not automatically shut off after a predetermined period of time regardless of any use during that period of time.
For example, U.S. Pat. No. 4,673,798, to Contri et al. describes a complex control and automatic shut-off circuit for an electric curling iron. The Contri et al. controller operates by measuring the actual temperature of the hair curler barrel against preset high and low temperature thresholds and indicates when those temperature levels are exceeded. In addition, the Contri et al. controller automatically shuts off the curler when a preset time period, initiated by operation of the curling iron's clamp, is exceeded. However, the Contri et al. arrangement is complex. The circuitry depends upon four factors to control and indicate two states of the appliance. In addition, the Contri et al. automatic shut-off design does not avoid potential safety risks. Because the shut-off control depends upon movement of the hair clamp, if the appliance is mistakenly dropped or manipulated by a small child, the appliance will automatically turn back on.
Other less complex circuits than Contri et al. fail to indicate or control both the ready and automatic shut-off conditions of an appliance. The Albinger, Jr. et al. patent, U.S. Pat. No. 4,745,260, for example, uses a motion sensor and electronic timer to control an automatic shut-off circuit for an electric iron. Thus, when the iron has not been moved for a predetermined period of time, the Albinger et al. device automatically turns off the appliance. However, the Albinger et al. device fails to indicate when the iron is ready for use.
The Conrad et al. patent, U.S. Pat. No. 4,347,428, provides for an electric iron having three indicator lights which respectively represent sufficient, insufficient or excessive temperature levels. Conrad et al., however, does not contain circuitry for automatically switching off the appliance after a long period of non-use.
Munshaw, U.S. Pat. No. 4,418,268, also shows an electrical appliance control having a multi-mode indicator.
However, the Munshaw controller does not automatically shut off the appliance when the appliance is not in use.
The invention set forth herein, therefore, provides for an apparatus that effectively controls and indicates an appliance's readiness and automatically shuts off the electrical appliance through a simple circuit design without the safety pitfalls outlined above.